The present invention relates to liquid dye formulations that include liquid solvent dyes in non-petroleum based solvent systems such as vegetable oil esters.
Liquid Dye formulations or colorants have widespread commercial uses. In a liquid context, certain dye formulations are particularly useful, for example, writing inks (e.g., soft tip markers), printing inks (e.g., in ink jet printers) and color coding various petroleum fractions for tax purposes, octane/cetane levels and to monitor levels of fuel additives. Liquid dyes have become commercially popular due to their high tinctorial strength (i.e., the amount of color per unit colorant) and ease of handling at the point of application versus powder dyes.
Liquid solvent dyes generally have a tar like consistency at room temperature. Thus, viscosity depressant solvent systems are used to dilute these solvent dyes for manufacturing commercially viable dye formulations.
Those of ordinary skill in the art will know that a dye is a substance that imparts color when dissolved in a substrate (i.e., the product that is dyed). Solvent dyes are soluble in a variety of substrates but insoluble in water. Some of the substrates they are used to color are organic solvents, hydrocarbon fuels, waxes, lubricants and plastics. Their molecules are typically nonpolar or of minimal polarity, and they do not undergo ionization. As defined in Hawley's Condensed Chemical Dictionary, Eleventh Edition, Solvent dyes are organosoluble dyes.
Historically, xylene (mixed and single isomers), high flash aromatic solvents, hydro-treated light naphthenic distillates have been the solvents of choice for oil soluble applications (e.g., petroleum-based applications). For non-petroleum applications, alcohols, straight and branched chain, glycols, glycol ethers, Mineral Spirits and NMP (i.e., N-Methyl Pyroldinone) have been the solvents of choice. These aforementioned solvent systems present workers and consumers exposure problems due to their toxicity profile. Similarly, the potential environmental impact has to be monitored as well. Government regulations are increasingly demanding that manufacturers investigate their processes and formulations to try to find “greener' alternative technology. Similarly, it is prudent to reduce the use of products whose precursor is crude oil.
Liquid dye formulations have typically used solvents that are amenable to their end use application. An example of this is Solvent Red 164 diluted with mineral oil. This is sold as Navipol Red 164 HF as well as other commercial brands. One of its principal uses is the coloration of automotive transmission fluid (i.e., substrate) to detect leaks in automobile transmissions. In this case, mineral oil is the solvent of choice due to its likeness to the substrate and its compatibility with automotive gaskets and seals.
Traditionally, viscosity depressant solvents were chosen based on their usefulness in the specific end use application and their acceptable solubility and liquid stability to the dye formulation. Thus, their toxicity as well as their impact on the environment was secondary to their functionality.
Recently, however, there has been greater emphasis on manufacturing environment-friendly dye formulations. Environmental programs such as REACH (i.e., Registration, Evaluation, Authorization and Restriction of Chemicals) are being implemented in the European Union. One of the mandates of the REACH program is for chemical manufacturers to systematically replace products containing chemicals that are toxic and harmful to the environment with less toxic products manufactured using improved “greener” technology.
As an example of solvent dye use, in the United States, refiners must adhere to the IRS regulation to mark all off road diesel fuel/heating oil with 26 PPM of Solvent Red 164 to monitor fuel excise tax evasion. Typically, petroleum-based solvents are used for preparing the dye formulations for this purpose. When these petroleum-based dye formulations are used as additives in diesel fuel or heating oil, it increases the total sulfur content of the fuel. This is becoming a problem, particularly for refiners in the United States, who must comply with the EPA (Environment Protection Agency) mandate of 15 PPM of sulfur or less.
In view of the aforementioned, a need exists for non-petroleum based solvents that are useful in specific end use applications (e.g., have acceptable solubility and liquid stability to existing commercially available liquid dyes) but are also environmentally safe and less toxic and do not exceed present or proposed mandates by regulatory agencies.